One thing straight away: UPGRADE YOUR RAM. 1333 on an AMD rig is asking for trouble. 1600MHz or better. Then upgrade your CPU to and Athlon X4 860K since you are using a 260X there is no need for the A8. Plus the 860K is a newer tech. Maybe boost the GPU to the 270X or 285.
Not sure if you want multiple screens or not. That's the tower changes I'd make. I would have gone with the R9 290 but I didn't want to stress the CX500 out too much.
I reckon sell your existing rig (get around $300 for it). Then get something like this.
http://pcpartpicker.com/user/deejeta/saved/X9Zj4D - just keep your HDD and maybe the cpu cooler (if you do use the nb or noctua fan on it if you havent already). PSU is overkill but your budget is high and its fully modular and it'll be uber quiet for the load you'd be putting it under. Also that kingston ssd is a time bomb, so I'd part ways with it while you can.
Spend whats left on a nice ips monitor setup + some nice speakers / usb DAC etc.